Magnetic random access memory

ABSTRACT

A data selection line (write line) is disposed right on a MTJ element. Upper and side surfaces of the data selection line are coated with yoke materials which have a high permeability. The yoke materials are separated from each other by a barrier layer. Similarly, a write word line is disposed right under the MTJ element. The lower and side surfaces of the write word line are also coated with the yoke materials which have the high permeability. The yoke materials on the lower and side surfaces of the write word line are also separated from each other by the barrier layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2002-301940, filed Oct.16, 2002, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a magnetic random access memory(MRAM) in which a MTJ (Magnetic Tunnel Junction) element for storing“1”, “0”-information by a TMR effect is used to constitute a memorycell.

[0004] 2. Description of the Related Art

[0005] In recent years, a large number of memories in which informationis stored by a new principle have been proposed. Among the memories,there is a memory which uses a tunneling magneto resistive (hereinafterreferred to as TMR) effect proposed by Roy Scheuerlein et al. (refer toISSCC2000 Technical Digest p. 128 “A 10 ns Read and Write Non-VolatileMemory Array Using a Magnetic Tunnel Junction and FET Switch in eachCell”).

[0006] In a magnetic random access memory, a MTJ element stores “1”,“0”-information. As shown in FIG. 1, the MTJ element includes astructure in which an insulating layer (tunneling barrier) is held bytwo magnetic layers (ferromagnetic layers). The information to be storedin the MTJ element is judged by judging whether or not directions ofspin of two magnetic layers are parallel or anti-parallel.

[0007] Here, as shown in FIG. 2, “parallel” means that the directions ofspin of two magnetic layers (direction of magnetization) are the same,and “anti-parallel” means that the directions of spin of two magneticlayers are opposite to each other (the directions of arrows indicate thedirections of spin).

[0008] It is to be noted that an anti-ferromagnetic layer is usuallydisposed in one of two magnetic layers. The anti-ferromagnetic layer isa member for fixing the spin direction of one magnetic layer andchanging only the spin direction of the other magnetic layer to easilyrewrite the information.

[0009] The magnetic layer whose spin direction is fixed is referred toas a fixed or pinned layer. Moreover, the magnetic layer whose spindirection can freely be changed in accordance with write data isreferred to as a free or storage layer.

[0010] As shown in FIG. 2, when the spin directions of two magneticlayers are parallel to each other, tunnel resistance of the insulatinglayer (tunneling barrier) held between two magnetic layers is lowest.This state is a “1”-state. Moreover, when the spin directions of twomagnetic layers are anti-parallel, the tunnel resistance of theinsulating layer (tunneling barrier) held between two magnetic layers ishighest. This state is a “0”-state.

[0011] A write operation principle with respect to the MTJ element willnext briefly be described with reference to FIG. 3.

[0012] The MTJ element is disposed in an intersection of a write wordline and data selection line (read/write bit line) which intersect witheach other. Moreover, the write is achieved by passing a current intothe write word line and data selection line, and using a magnetic fieldformed by the current flowing through both wires to set the spindirection of the MTJ element to be parallel or anti-parallel.

[0013] For example, when a magnetization easy axis of the MTJ element isan X-direction, the write word line extends in the X-direction, and thedata selection line extends in a Y-direction crossing at right angles tothe X-direction, a current directed in one direction is passed throughthe write word line at a write time, and a current directed in one orthe other direction is passed through the data selection line inaccordance with the write data.

[0014] When the current directed in one direction is passed through thedata selection line, the spin direction of the MTJ element becomesparallel (“l”-state). On the other hand, when the current directed inthe other direction is passed through the data selection line, the spindirection of the MTJ element becomes anti-parallel (“0”-state).

[0015] A mechanism in which the spin direction of the MTJ elementchanges is as follows.

[0016] When a magnetic field Hx is applied in a long-side (easy-axis)direction of the MTJ element as shown by a TMR curve of FIG. 4, theresistance value of the MTJ element changes, for example, by about 17%.This change ratio, that is, a ratio of the resistance values before andafter the change is referred to as an MR ratio.

[0017] It is to be noted that the MR ratio changes by properties of themagnetic layer. At present, the MTJ element whose MR ratio is about 50%is obtained.

[0018] A synthetic magnetic field of the magnetic field Hx of aneasy-axis direction and magnetic field Hy of a hard-axis direction isapplied to the MTJ element. As shown by a solid line of FIG. 5, the sizeof the magnetic field Hx of the easy-axis direction necessary forchanging the resistance value of the MTJ element also changes by thesize of the magnetic field Hy of the hard-axis direction. Thisphenomenon can be used to write data only into the MTJ element whichexists in the intersection of the selected write word line and dataselection line among memory cells arranged in an array form.

[0019] This state will further be described with reference to Astroidcurve of FIG. 5.

[0020] The Astroid curve of the MTJ element is shown, for example, by asolid line of FIG. 5. That is, when the size of the synthetic magneticfield of the magnetic field Hx of the easy-axis direction and themagnetic field Hy of the hard-axis direction is outside the Astroidcurve (solid line) (e.g., in positions of black circles), the spindirection of the magnetic layer can be reversed.

[0021] Conversely, when the size of the synthetic magnetic field of themagnetic field Hx of the easy-axis direction and the magnetic field Hyof the hard-axis direction is inside the Astroid curve (solid line)(e.g., in positions of white circles), the spin direction of themagnetic layer cannot be reversed.

[0022] Therefore, when the sizes of the magnetic field Hx of theeasy-axis direction and the magnetic field Hy of the hard-axis directionare changed, and the position of the size of the synthetic magneticfield in an Hx-Hy plane is changed, the write of the data with respectto the MTJ element can be controlled.

[0023] A read operation can easily be performed by passing a currentthrough the selected MTJ element, and detecting the resistance value ofthe MTJ element.

[0024] For example, a switch element is connected in series to the MTJelement, and only the switch element connected to a selected read wordline is turned on to form a current path. As a result, since the currentflows only through the selected MTJ element, the data of the MTJ elementcan be read out.

[0025] In the magnetic random access memory, as described above, thedata write is performed by passing the write current through the writeword line and data selection line (read/write bit line) and allowing asynthetic magnetic field Hx+Hy generated thereby to act on the MTJelement.

[0026] Therefore, to efficiently perform the data write, it is importantto efficiently apply the synthetic magnetic field Hx+Hy to the MTJelement. When the synthetic magnetic field Hx+Hy is efficiently appliedto the MTJ element, reliability of the write operation is enhanced,further a write current is reduced, and low power consumption can berealized.

[0027] However, an effective device structure for allowing the syntheticmagnetic field Hx+Hy generated by the write currents flowing through thewrite word line and data selection line to efficiently act on the MTJelement has not been sufficiently studied. That is, for the devicestructure, it naturally needs to be studied whether the syntheticmagnetic field Hx+Hy is actually efficiently applied to the MTJ element.Furthermore, in a manufacturing process aspect, it needs to be studiedwhether or not the structure can easily be manufactured.

[0028] In recent years, as a technique of efficiently applying themagnetic fields Hx, Hy to the MTJ element, the device structure has beenstudied in which a yoke material having a function of suppressing spreadof the magnetic field is disposed around a write line (refer to U.S.Pat. No. 6,174,737).

[0029] The yoke material has high permeability, and magnetic flux has aproperty of being concentrated on a material which has the highpermeability. Therefore, when the yoke material is used as a tractionmaterial of a magnetic force line, the magnetic fields Hx, Hy generatedby the write current flowing through the write line can efficiently beconcentrated on the MTJ element at a write operation time.

[0030] The yoke material has a function of suppressing the spread of themagnetic field as described above. This is based on a prerequisite thatfilm thickness and magnetic domain of the yoke material are accuratelycontrolled. That is, when dispersion is generated in the film thicknessof the yoke material arranged around the write line, and the magneticdomain is not orderly aligned, an effect of the yoke material inbunching a magnetic force line is reduced, and it becomes impossible toefficiently apply the magnetic fields Hx, Hy to the MTJ element.

BRIEF SUMMARY OF THE INVENTION

[0031] According to one aspect of the present invention, there isprovided a magnetic random access memory comprising: a memory cell whichuses a magneto resistive effect to store data; a first write line whichis disposed right on the memory cell and which extends in a firstdirection; a second write line which is disposed right under the memorycell and which extends in a second direction intersecting with the firstdirection; a first yoke material with which an upper surface of thefirst write line is coated; a second yoke material with which a sidesurface of the first write line is coated; and a first barrier layerwhich is disposed between the first yoke material and first write lineand between the second yoke material and first write line and whichseparates the first yoke material from the second yoke material.

[0032] According to another aspect of the present invention, there isprovided a magnetic random access memory comprising: a memory cell whichuses a magneto resistive effect to store data; a first write line whichis disposed right on the memory cell and which extends in a firstdirection; a second write line which is disposed right under the memorycell and which extends in a second direction intersecting with the firstdirection; a first yoke material with which a lower surface of thesecond write line is coated; a second yoke material with which a sidesurface of the second write line is coated; and a first barrier layerwhich is disposed between the first yoke material and first write lineand between the second yoke material and first write line and whichseparates the first yoke material from the second yoke material.

[0033] According to further aspect of the present invention, there isprovided a manufacturing method of a magnetic random access memory,comprising: a step of forming a first yoke material on an insulatinglayer on a semiconductor substrate; a step of forming a conductivematerial on the first yoke material; a step of patterning the conductivematerial and first yoke material to form a write line whose lowersurface is coated with the first yoke material; a step of forming afirst barrier layer with which the write line is coated; a step offorming a second yoke material with which the write line is coated onthe first barrier layer; a step of etching the first barrier layer andsecond yoke material to allow the first barrier layer and second yokematerial to remain on the side surface of the write line; and a step offorming a memory cell which uses a magneto resistive effect to storedata right on the first write line.

[0034] According to still further aspect of the present invention, thereis provided a manufacturing method of a magnetic random access memory,comprising: a step of forming a memory cell which uses a magnetoresistive effect to store data on an insulating layer on a semiconductorsubstrate; a step of forming a conductive material right on the memorycell; a step of forming a first yoke material on the conductivematerial; a step of patterning the first yoke material and conductivematerial to form a write line whose upper surface is coated with thefirst yoke material; a step of forming a first barrier layer with whichthe write line is coated; a step of forming a second yoke material withwhich the write line is coated on the first barrier layer; and a step ofetching the first barrier layer and second yoke material to allow thefirst barrier layer and second yoke material to remain on the sidesurface of the write line.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0035]FIG. 1 is a diagram showing a structure example of a MTJ element;

[0036]FIG. 2 is a diagram showing two states of the MTJ element;

[0037]FIG. 3 is a diagram showing a write operation principle of amagnetic random access memory;

[0038]FIG. 4 is a diagram showing a TMR curve;

[0039]FIG. 5 is a diagram showing an Astroid curve;

[0040]FIG. 6 is a sectional view of the magnetic random access memoryaccording to a first reference example;

[0041]FIG. 7 is a sectional view of the magnetic random access memoryaccording to the first reference example;

[0042]FIG. 8 is a sectional view of the magnetic random access memoryaccording to a second reference example;

[0043]FIG. 9 is a sectional view of the magnetic random access memoryaccording to the second reference example;

[0044]FIG. 10 is a sectional view of the magnetic random access memoryaccording to a first embodiment;

[0045]FIG. 11 is a sectional view of the magnetic random access memoryaccording to the first embodiment;

[0046]FIG. 12 is a sectional view showing one step of a manufacturingmethod of the memory according to the first embodiment;

[0047]FIG. 13 is a sectional view showing one step of the manufacturingmethod of the memory according to the first embodiment;

[0048]FIG. 14 is a sectional view showing one step of the manufacturingmethod of the memory according to the first embodiment;

[0049]FIG. 15 is a sectional view showing one step of the manufacturingmethod of the memory according to the first embodiment;

[0050]FIG. 16 is a sectional view showing one step of the manufacturingmethod of the memory according to the first embodiment;

[0051]FIG. 17 is a sectional view showing one step of the manufacturingmethod of the memory according to the first embodiment;

[0052]FIG. 18 is a sectional view of the magnetic random access memoryaccording to a second embodiment;

[0053]FIG. 19 is a sectional view of the magnetic random access memoryaccording to the second embodiment;

[0054]FIG. 20 is a sectional view showing one step of the manufacturingmethod of the memory according to the second embodiment;

[0055]FIG. 21 is a sectional view showing one step of the manufacturingmethod of the memory according to the second embodiment;

[0056]FIG. 22 is a sectional view showing one step of the manufacturingmethod of the memory according to the second embodiment;

[0057]FIG. 23 is a sectional view showing one step of the manufacturingmethod of the memory according to the second embodiment;

[0058]FIG. 24 is a sectional view showing one step of the manufacturingmethod of the memory according to the second embodiment;

[0059]FIG. 25 is a sectional view showing one step of the manufacturingmethod of the memory according to the second embodiment;

[0060]FIG. 26 is a sectional view of the magnetic random access memoryaccording to a third embodiment;

[0061]FIG. 27 is a sectional view of the magnetic random access memoryaccording to the third embodiment;

[0062]FIG. 28 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0063]FIG. 29 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0064]FIG. 30 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0065]FIG. 31 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0066]FIG. 32 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0067]FIG. 33 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0068]FIG. 34 is a sectional view showing one step of the manufacturingmethod of the memory according to the third embodiment;

[0069]FIG. 35 is a sectional view of the magnetic random access memoryaccording to a fourth embodiment;

[0070]FIG. 36 is a sectional view of the magnetic random access memoryaccording to the fourth embodiment;

[0071]FIG. 37 is a sectional view of the magnetic random access memoryaccording to a fifth embodiment;

[0072]FIG. 38 is a sectional view of the magnetic random access memoryaccording to a sixth embodiment; and

[0073]FIG. 39 is a sectional view of the magnetic random access memoryaccording to a seventh embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0074] A magnetic random access memory according to embodiments of thepresent invention will be described hereinafter in detail with referenceto the drawings.

1. FIRST REFERENCE EXAMPLE

[0075] A device structure as a prerequisite of the present inventionwill first be described before the magnetic random access memoryaccording to an example of the present invention.

[0076] It is to be noted that the device structure is described for easeof understanding of the embodiment of the present invention, and thepresent invention is not limited to the device structure.

[0077]FIGS. 6 and 7 show the device structure as the prerequisite of theexample of the present invention.

[0078] Element separation insulating layers 12 including a shallowtrench isolation (STI) structure are formed in a semiconductor substrate(e.g., a p-type silicon substrate, p-type well region, and the like) 11.A region surrounded with the element separation insulating layers 12 isan element region in which a read selection switch (e.g., MOStransistor, diode, and the like) is formed.

[0079] In the device structure of FIG. 6, the read selection switch isconstituted of an MOS transistor (n-channel type MOS transistor). A gateinsulating layer 13, gate electrode 14, and side wall insulating layers15 are formed on the semiconductor substrate 11. The gate electrode 14extends in an X-direction, and functions as a read word line forselecting a read cell (MTJ element) at a read operation time.

[0080] A source region (e.g., n-type diffusion layer) 16-S and drainregion (e.g., n-type diffusion layer) 16-D are formed in thesemiconductor substrate 11. The gate electrode (read word line) 14 isdisposed in a channel region between the source region 16-S and drainregion 16-D.

[0081] In the device structure of FIG. 7, the read selection switch isconstituted of the diode. A cathode region (e.g., n-type diffusionlayer) 16 a and anode region (e.g., p-type diffusion layer) 16 b areformed in the semiconductor substrate 11.

[0082] One of metal layers constituting a first metal wiring layerfunctions as an intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as a source line18B (in FIG. 6) or read word line 18B (in FIG. 7).

[0083] In the device structure of FIG. 6, the intermediate layer 18A iselectrically connected to the drain region 16-D of the read selectionswitch (MOS transistor) by a contact plug 17A. The source line 18B iselectrically connected to the source region 16-S of the read selectionswitch via a contact plug 17B. The source line 18B extends in anX-direction similarly as the gate electrode (read word line) 14.

[0084] In the device structure of FIG. 7, the intermediate layer 18A iselectrically connected to the anode region 16 b of the read selectionswitch (diode) by the contact plug 17A. The read word line 18B iselectrically connected to the cathode region 16 a of the read selectionswitch via the contact plug 17B. The read word line 18B extends in theX-direction.

[0085] One of metal layers constituting a second metal wiring layerfunctions as an intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as a read wordline 20B. The intermediate layer 20A is electrically connected to theintermediate layer 18A by a contact plug 19. The read word line 20Bextends, for example, in the X-direction.

[0086] One of metal layers constituting a third metal wiring layerfunctions as a lower electrode 22 of a MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bya contact plug 21. The MTJ element 23 is mounted on the lower electrode22. Here, the MTJ element 23 is disposed right on the write word line20B, and formed in a rectangular shape long in the X-direction(magnetization easy axis is the X-direction).

[0087] One of metal layers constituting a fourth metal wiring layerfunctions as a data selection line (read/write bit line) 24. The dataselection line 24 is electrically connected to the MTJ element 23, andextends in a Y-direction.

[0088] It is to be noted that the structure of the MTJ element 23 is notespecially limited. The structure may be the structure shown in FIG. 1or any other structure. Moreover, the MTJ element 23 may also be of amulti-valued storage type in which data of a plurality of bits can bestored.

[0089] A ferromagnetic layer of the MTJ element 23 is not especiallylimited, and examples of a usable material include Fe, Co, Ni or analloy of these metals, magnetite in spin polarization ratio, oxides suchas CrO₂, RXMnO_(3-y) (R: rare earth metals, X: Ca, Ba, Sr), and Heusleralloys such as NiMnSb, PtMnSb.

[0090] Even with the ferromagnetic layer which contains some amount ofnonmagnetic elements such as Ag, Cu, Au, Al, Mg, Si, Bi, Ta, B, C, 0, N,Pd, Pt, Zr, Ir, W, Mo, Nb, as long as ferromagnetism is not lost, thereis not any problem.

[0091] If the ferromagnetic layer becomes excessively thin,super-paramagnetism results. To solve the problem, the ferromagneticlayer needs to have a thickness to such an extent that at least thesuper-paramagnetism does not result. Concretely, the thickness of theferromagnetic layer is set to 0.1 nm or more, preferably in a range of0.4 nm to 100 nm.

[0092] As an anti-ferromagnetic layer of the MTJ element 23, forexample, Fe—Mn, Pt—Mn, Pt—Cr—Mn, Ni—Mn, Ir—Mn, NiO, Fe₂O₃, and the likecan be used.

[0093] As an insulating layer (tunneling barrier) of the MTJ element 23,dielectric materials such as Al₂O₃, SiO₂, MgO, AlN, Bi₂O₃, MgF₂, CaF₂,SrTiO₂, and AlLaO₃ can be used. Even when there is oxygen loss, nitrogenloss, or fluorine loss in these materials, there is no problem.

[0094] The thickness of the insulating layer (tunneling barrier) ispreferably as small as possible, but there is not especially adetermined limitation for realizing the function. Additionally, thethickness of the insulating layer is set to 10 nm or less in amanufacturing process.

2. SECOND REFERENCE EXAMPLE

[0095] A device structure proposed with respect to the device structureof the first reference example in order to efficiently concentrate themagnetic field on the MTJ element will next be described.

[0096]FIGS. 8 and 9 show the device structure as the prerequisite of theexample of the present invention. It is to be noted that FIG. 8 shows asection of the Y-direction, and FIG. 9 shows a section of theX-direction of a MTJ element portion of FIG. 8. The X-direction crossesat right angles to the Y-direction.

[0097] The element separation insulating layers 12 including the STIstructure are formed in the semiconductor substrate (e.g., the p-typesilicon substrate, p-type well region, and the like) 11. The regionsurrounded with the element separation insulating layers 12 is theelement region in which the read selection switch (e.g., MOS transistor)is formed.

[0098] In the device structure of the example, the read selection switchis constituted of the MOS transistor (n-channel type MOS transistor).The gate insulating layer 13, gate electrode 14, and side wallinsulating layers 15 are formed on the semiconductor substrate 11. Thegate electrode 14 extends in the X-direction, and functions as the readword line for selecting the read cell (MTJ element) at the readoperation time.

[0099] The source region (e.g., n-type diffusion layer) 16-S and drainregion (e.g., n-type diffusion layer) 16-D are formed in thesemiconductor substrate 11. The gate electrode (read word line) 14 isdisposed on the channel region between the source region 16-S and drainregion 16-D.

[0100] One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

[0101] The intermediate layer 18A is electrically connected to the drainregion 16-D of the read selection switch (MOS transistor) by the contactplug 17A. The source line 18B is electrically connected to the sourceregion 16-S of the read selection switch via the contact plug 17B. Thesource line 18B extends in the X-direction similarly as the gateelectrode (read word line) 14.

[0102] One of the metal layers constituting the second metal wiringlayer functions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

[0103] In the device structure of the present example, the lower andside surfaces of the intermediate layer 20A and write word line 20B arecoated with the material having the high permeability, that is, yokematerials 25A, 25B. The yoke materials 25A, 25B for use herein arelimited to the materials which have conductivity.

[0104] A magnetic flux has a property of being concentrated on thematerial which has the high permeability. Therefore, when the materialhaving the high permeability is used as a traction material of amagnetic force line, a magnetic field Hy generated by a write currentflowing through the write word line 20B can efficiently be concentratedon the MTJ element 23 at a write operation time.

[0105] The present object can sufficiently be achieved, when the lowerand side surfaces of the write word line 20B are coated with the yokematerial. Additionally, in actual, the yoke materials are formed on thelower and side surfaces of the intermediate layer 20A. This is becausethe intermediate layer 20A and write word line 20B are simultaneouslyformed as the second metal wiring layer.

[0106] One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

[0107] One of the metal layers constituting the fourth metal wiringlayer functions as the data selection line (read/write bit line) 24. Thedata selection line 24 is electrically connected to the MTJ element 23,and extends in the Y-direction.

[0108] In the device structure of the present example, the upper andside surfaces of the data selection line 24 are coated with the materialhaving the high permeability, that is, a yoke material 26. As shown inFIGS. 8 and 9, the yoke material 26 for use herein can be constituted ofa material which has conductivity, or may also be constituted of amaterial which has insulation property.

[0109] The yoke material 26 can be constituted of, for example, NiFe,CoFe, amorphous-CoZrNb, FeAlSi, FeNx, and the like.

[0110] As described above, the magnetic flux has the property of beingconcentrated on the material which has the high permeability. Therefore,when the material having the high permeability is used as the tractionmaterial of the magnetic force line, a magnetic field Hx generated bythe write current flowing through the data selection line 24 canefficiently be concentrated on the MTJ element 23 at the write operationtime.

[0111] It is to be noted that the structure of the MTJ element 23 is notespecially limited. The structure may be the structure shown in FIG. 1or any other structure. Moreover, the MTJ element 23 may also be of themulti-valued storage type in which data of a plurality of bits can bestored.

[0112] In this device structure, the yoke material 25B is formed on thelower and side surfaces of the write word line 20B disposed right underthe MTJ element 23. Moreover, the yoke material 26 is formed on theupper and side surfaces of the data selection line (read/write bit line)24 disposed right on the MTJ element 23.

[0113] However, in this case, the yoke material 25B around the writeword line 20B is also formed in a lower corner portion, and the yokematerial 26 around the data selection line 24 is also formed in an uppercorner portion.

[0114] For the yoke materials 25B, 26 of the corner portions of thewrite word line 20B and data selection line 24, it is very difficult tocontrol the film thickness in a manufacturing time (e.g., sputteringtime), and this causes disorder in arrangement of magnetic domain of theyoke materials 25B, 26. As a result, convergence effect of the magneticfield by the yoke materials 25B, 26 is reduced, and it becomesimpossible to efficiently supply the magnetic field to the MTJ element.

[0115] 3. First Embodiment

[0116] Embodiments of the present invention will next be described basedon the above-described first and second reference examples. Theembodiment of the present invention relates to the device structure ofthe magnetic random access memory in which the magnetic domain of theyoke material disposed around the write line can easily be controlledand the magnetic field can efficiently be concentrated on the MTJelement.

[0117] (1) Structure

[0118]FIGS. 10 and 11 show the device structure of the magnetic randomaccess memory according to a first embodiment of the present invention.It is to be noted that FIG. 10 shows the section of the Y-direction, andFIG. 11 shows the section of the X-direction of the MTJ element portionof FIG. 10. The X-direction crosses at right angles to the Y-direction.

[0119] The device structure of the present embodiment is characterizedin that the yoke material disposed on the lower or upper surface of thewrite line is separated from the yoke material disposed on the sidesurface of the write line by a barrier layer and the yoke materialextending to the side surface from the lower or upper surface isprevented from being formed on the corner portion of the write line.

[0120] That is, the magnetic domain control of the yoke materialdisposed on the lower or upper surface of the write line and themagnetic domain control of the yoke material disposed on the sidesurface of the write line are separately performed, thereby the magneticdomain control of the yoke material around the write line isfacilitated, and the application efficiency of the magnetic field withrespect to the MTJ element is enhanced.

[0121] The element separation insulating layers 12 including the STIstructure are formed in the semiconductor substrate (e.g., the p-typesilicon substrate, p-type well region, and the like) 11. The regionsurrounded with the element separation insulating layers 12 is theelement region in which the read selection switch is formed.

[0122] The read selection switch is constituted of the MOS transistor(n-channel type MOS transistor). The gate insulating layer 13, gateelectrode 14, and side wall insulating layers 15 are formed on thesemiconductor substrate 11. The gate electrode 14 extends in theX-direction, and functions as the read word line for selecting the readcell (MTJ element) at the read operation time.

[0123] The source region (e.g., n-type diffusion layer) 16-S and drainregion (e.g., n-type diffusion layer) 16-D are formed in thesemiconductor substrate 11. The gate electrode (read word line) 14 isdisposed on the channel region between the source region 16-S and drainregion 16-D.

[0124] One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

[0125] The intermediate layer 18A is electrically connected to the drainregion 16-D of the read selection switch (MOS transistor) by the contactplug 17A. The source line 18B is electrically connected to the sourceregion 16-S of the read selection switch via the contact plug 17B. Thesource line 18B extends in the X-direction, for example, similarly asthe gate electrode (read word line) 14.

[0126] One of the metal layers constituting the second metal wiringlayer functions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

[0127] The lower surfaces of the intermediate layer 20A and write wordline 20B are coated with the material having the high permeability, thatis, yoke materials 25A1, 25B1. The yoke materials 25A1, 25B1 for useherein are limited to the materials which have conductivity.

[0128] Barrier metals (e.g., Ti, TiN or a lamination of these) 27 a, 27b are formed right under the yoke materials 25A1, 25B1, and barriermetals (e.g., Ti, TiN or the lamination of these) 27 c, 27 d are formedright on the barrier metals. That is, the yoke materials 25A1, 25B1 areheld between the barrier metals 27 a, 27 b, 27 c, 27 d.

[0129] The barrier metals 27 a, 27 b, 27 c, 27 d prevent atomsconstituting the yoke materials 25A1, 25B1 from being diffused.

[0130] Moreover, the side surfaces of the intermediate layer 20A andread word line 20B are also coated with the materials which have highpermeability, that is, yoke materials 25A2, 25B2. Here, the yokematerials 25A2, 25B2 for use herein may have either conductivity orinsulation property.

[0131] When the yoke materials 25A1, 25B1, 25A2, 25B2 are used as thetraction material of the magnetic force line, the magnetic field Hygenerated by the write current flowing through the write word line 20Bcan efficiently be concentrated on the MTJ element 23.

[0132] Barrier layers 28 a, 28 b (e.g., Ti, TiN or the lamination ofthese, or Ta, TaN or the lamination of these) are formed on the sidesurfaces of the intermediate layer 20A and write word line 20B. Thebarrier layers 28 a, 28 b separate the yoke materials 25A1, 25B1 withwhich the lower surfaces of the intermediate layer 20A and write wordline 20B are coated from the yoke materials 25A2, 25B2 with which theside surfaces are coated.

[0133] The barrier layers 28 a, 28 b may have either the conductivity orinsulation property. Moreover, the barrier layers 28 a, 28 b may havethe same functions as those of the barrier metals 27 a, 27 b. In thiscase, since the barrier layers 28 a, 28 b sufficiently fulfill adiffusion prevention function of atoms, each of the layers preferablyhas a thickness of at least about 20 nm.

[0134] One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

[0135] One of the metal layers constituting the fourth metal wiringlayer functions as the data selection line (read/write bit line) 24. Thedata selection line 24 is electrically connected to the MTJ element 23,and extends in the Y-direction.

[0136] The upper surface of the data selection line 24 is coated withthe material having the high permeability, that is, the yoke material26. The yoke material 26 for use herein may have either conductivity orinsulation property.

[0137] A barrier metal (e.g., Ti, TiN or the lamination of these) 29 forpreventing the atoms from being diffused is formed on the lower surfaceof the data selection line 24, and a barrier layer (e.g., Ti, TiN or thelamination of these, or Ta, TaN or the lamination of these) 30 is formedon the upper surface of the data selection line.

[0138] Moreover, the side surface of the data selection line 24 is alsocoated with the material which has the high permeability, that is, yokematerials 32. The yoke material 32 for use herein may have eitherconductivity or insulation property.

[0139] When the yoke materials 26, 32 are used as the traction materialof the magnetic force line, the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beconcentrated on the MTJ element 23.

[0140] Barrier layers 31 (e.g., Ti, TiN or the lamination of these, orTa, TaN or the lamination of these) are formed on the side surfaces ofthe data selection line 24. The barrier layers 31 separate the yokematerial 26 with which the upper surface of the data selection line 24is coated from the yoke materials 32 with which the side surfaces of thedata selection line are coated.

[0141] The barrier layers 30, 31 may have either the conductivity orinsulation property. Moreover, the barrier layers 30, 31 may have thesame functions as those of the barrier metal 29. Since the barrierlayers 30, 31 sufficiently fulfill the diffusion prevention function ofatoms, each of the layers preferably has a thickness of at least about20 nm.

[0142] It is to be noted that the structure of the MTJ element 23 is notespecially limited. The structure may be the structure shown in FIG. 1or any other structure. Moreover, the MTJ element 23 may also be of themulti-valued storage type in which data of a plurality of bits can bestored.

[0143] (2) Manufacturing Method

[0144] A manufacturing method of the magnetic random access memoryaccording to the first embodiment of the present invention will next bedescribed.

[0145] First, as shown in FIG. 12, known methods such as a photoengraving process (PEP) method, chemical vapour deposition (CVD) method,and chemical mechanical polishing (CMP) process are used to form theelement separation insulating layer 12 including the STI structure inthe semiconductor substrate 11.

[0146] Moreover, the MOS transistor as the read selection switch isformed in the element region surrounded with the element separationinsulating layer 12.

[0147] After forming the gate insulating layer 13 and gate electrode(read word line) 14 by CVD method, PEP method, and reactive ion etching(RIE) method, the source region 16-S and drain region 16-D are formed byan ion implantation method, so that the MOS transistor can easily beformed. It is to be noted that the side wall insulating layers 15 mayalso be formed on side wall portions of the gate electrode 14 by the CVDand RIE methods.

[0148] Thereafter, an insulating layer 28A with which the MOS transistoris completely coated is formed by the CVD method. Moreover, the surfaceof the insulating layer 28A is flatted using the CMP method. Contactholes reaching the source region 16-S and drain region 16-D of the MOStransistor are formed in the insulating layer 28A using the PEP and RIEmethods.

[0149] Barrier metals (e.g., Ti, TiN, or the lamination of these) 51 areformed on the insulating layer 28A and on the inner surfaces of thecontact holes by a sputter method. Subsequently, conductive materials(e.g., a conductive polysilicon film including impurities, metal film,and the like) with which the contact holes are completely filled areformed on the insulating layer 28A by the sputter method. Moreover, bythe CMP method, the conductive materials and barrier metals 51 arepolished, and the contact plugs 17A, 17B are formed.

[0150] An insulating layer 28B is formed on the insulating layer 28Ausing the CVD method. The PEP and RIE methods are used to form wiringtrenches in the insulating layer 28B. The sputter method is used to formbarrier metals (e.g., Ti, TiN, or the lamination of these) 52 on theinsulating layer 28B and on the inner surfaces of the wiring trenches.Subsequently, the conductive materials (e.g., metal films such asaluminum and copper) with which the wiring trenches are completelyfilled are formed on the insulating layer 28B by the sputter method.Thereafter, by the CMP method, the conductive materials and barriermetals 52 are polished, and the intermediate layer 18A and source line18B are formed.

[0151] Subsequently, the CVD method is used to form an insulating layer28C on the insulating layer 28B. The PEP and RIE methods are used toform via holes in the insulating layer 28C. By the sputter method,barrier metals (e.g., Ti, TiN, or the lamination of these) 53 are formedon the insulating layer 28C and on the inner surfaces of the via holes.Subsequently, by the sputter method, the conductive materials (e.g., themetal films such as aluminum and copper) with which the via holes arecompletely filled are formed on the insulating layer 28C. Thereafter, bythe CMP method, the conductive materials and barrier metals 53 arepolished, and a via plug 19 is formed.

[0152] Subsequently, as shown in FIG. 13, by the sputter method, thebarrier metals (e.g., a lamination of Ti (10 nm) and TiN (10 nm)) 27 a,27 b are formed on the insulating layer 28C. Subsequently, the sputtermethod is used to form the yoke materials (e.g., NiFe) 25A1, 25B1 whichhave the high permeability in a thickness of about 50 nm on the barriermetals 27 a, 27 b. Moreover, the sputter method is used to form barriermetals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27 c, 27 don the yoke materials 25A1, 25B1.

[0153] Furthermore, the sputter method is continuously used to form theconductive material (e.g., AlCu) in a thickness of about 250 nm on thebarrier metals 27 c, 27 d. Thereafter, the PEP and RIE methods are usedto etch the conductive materials, yoke materials 25A1, 25B1, and barriermetals 27 a, 27 b, 27 c, 27 d, so that the intermediate layer 20A andwrite word line 20B are formed.

[0154] Additionally, the sputter method is used to form the barrierlayers (e.g., a lamination of Ta (10 nm) and TaN (10 nm)) 28 a, 28 bwith which the intermediate layer 20A and write word line 20B arecoated. The sputter method is continuously used to form the yokematerials (e.g., NiFe) 25A2, 25B2 which have the high permeability in athickness of about 50 nm on the barrier layers 28 a, 28 b.

[0155] Moreover, by the RIE method, the yoke materials 25A2, 25B2 andbarrier layers 28 a, 28 b are etched, so that the yoke materials 25A2,25B2 and barrier layers 28 a, 28 b remain only on the side wall portionsof the intermediate layer 20A and write word line 20B.

[0156] Thereafter, the CVD method is used to form an insulating layer29A with which the intermediate layer 20A and write word line 20B arecompletely coated on the insulating layer 28C. Moreover, the surface ofthe insulating layer 29A is flatted, for example, by the CMP method.

[0157] Subsequently, as shown in FIG. 14, the PEP and RIE methods areused to form the via holes which reach the intermediate layer 20A in theinsulating layer 29A. By the sputter method, barrier metals (e.g., Ti,TiN, or the lamination of these) 55 are formed on the insulating layer29A and on the inner surfaces of the via holes in a thickness of about10 nm. Subsequently, the conductive materials (e.g., the metal film suchas tungsten) with which the via holes are completely filled are formedon the insulating layer 29A by the CVD method. Thereafter, by the CMPmethod, the conductive materials and barrier metals 55 are polished, anda via plug 21 is formed.

[0158] The CVD method is used to form an insulating layer 30A on theinsulating layer 29A. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 30A. By the sputter method, theconductive materials (e.g., the metal films such as Ta) with which thewiring trenches are completely filled are formed on the insulating layer30A in a thickness of about 30 nm. Thereafter, by the CMP, theconductive materials are polished, and a local interconnect line (lowerelectrode of the MTJ element) 22 is formed.

[0159] The CVD method is used to successively deposit a plurality oflayers on the local interconnect line 22, and these plurality of layersare further patterned to form the MTJ elements 23.

[0160] The MTJ element 23 is constituted of a lamination film including,for example, Ta (about 40 nm), NiFe (about 10 nm), Al₂O₃ (about 2 nm),CoFe (about 10 nm), and IrMn (about 10 nm), or a lamination filmincluding NiFe (about 5 nm), IrMn (about 12 nm), CoFe (about 3 nm), AlOx(about 1.2 nm), CoFe (about 5 nm), and NiFe (about 15 nm).

[0161] Moreover, the CVD method is used to form an insulating layer 30Bwith which the MTJ element 23 is coated, and subsequently, theinsulating layer 30B on the MTJ element 23 is removed, for example, bythe CMP method. As a result, a topmost layer of the MTJ element 23 isexposed, and only the side surface of the MTJ element 23 is coated withthe insulating layer 30B.

[0162] It is to be noted that to constitute the topmost layer of the MTJelement 23 by Ta or W, the topmost layer of the MTJ element 23 isexposed, and subsequently the data selection line described later candirectly be formed.

[0163] Subsequently, as shown in FIG. 15, the barrier metal (e.g., thelamination of Ti (10 nm) and TiN (10 nm)) 29 is formed on the insulatinglayer 30B by the sputter method. Continuously, the conductive material(such as AlCu) is formed in a thickness of about 400 nm on the barriermetal 29 by the sputter method. Continuously, the barrier layer (e.g.,the lamination of Ta (10 nm) and TaN (10 nm)) 30 is formed on theconductive material by the sputter method.

[0164] Furthermore, the yoke material (such as NiFe) 26 which has thehigh permeability is continuously formed in a thickness of about 50 nmon the barrier layer 30 by the sputter method. Thereafter, the PEPmethod is used to form a resist pattern 33.

[0165] Additionally, the RIE method is used, and the resist pattern 33is used as a mask to etch the yoke material 26, barrier layer 30,conductive material, and barrier metal 29, so that the data selectionline (read/write bit line) 24 is formed.

[0166] Thereafter, the resist pattern 33 is removed.

[0167] Subsequently, as shown in FIG. 16, the barrier layer (e.g., thelamination of Ta (10 nm) and TaN (10 nm)) 31 with which the dataselection line 24 is coated is formed on the insulating layer 30B by thesputter method. Continuously, the yoke material (such as NiFe) 32 whichhas the high permeability is formed in a thickness of about 50 nm on thebarrier layer 31 by the sputter method.

[0168] Moreover, when the yoke material 32 and barrier layer 31 areetched by the RIE method, as shown in FIG. 17, the yoke material 32 andbarrier layer 31 remain only on the side wall portion of the dataselection line 24.

[0169] The magnetic random access memory of the first embodiment (FIGS.10 and 11) is completed by the above-described steps.

(3) CONCLUSION

[0170] As described above, according to the first embodiment, the lowersurface of the write word line 20B is coated with the yoke material25B1, and the side surface of the line is coated with the yoke material25B2. Moreover, since the yoke materials 25B1, 25B2 are separated fromeach other by the barrier layer 28 b, the yoke material covering thelower and side surfaces of the write word line is not formed in thelower corner portion of the write word line 20B.

[0171] Therefore, the magnetic domains of the yoke materials 25B1, 25B2are easily controlled, and the magnetic field Hy generated by the writecurrent flowing through the write word line 20B can efficiently beexerted onto the MTJ element 23.

[0172] Moreover, according to the first embodiment, the upper surface ofthe data selection line 24 is coated with the yoke material 26, and theside surface of the data selection line is coated with the yoke material32. Furthermore, since the yoke materials 26, 32 are separated from eachother by the barrier layer 31, the yoke material covering the upper andside surfaces of the data selection line is not formed in the uppercorner portion of the data selection line 24.

[0173] Therefore, the magnetic domains of the yoke materials 26, 32 areeasily controlled, and the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beexerted onto the MTJ element 23.

[0174] 4. Second Embodiment

[0175]FIGS. 18 and 19 show the device structure of the magnetic randomaccess memory according to a second embodiment of the present invention.It is to be noted that FIG. 18 shows the section of the Y-direction, andFIG. 19 shows the section of the X-direction of the MTJ element portionof FIG. 18. The X-direction crosses at right angles to the Y-direction.

[0176] The device structure of the present embodiment is characterizedin that the yoke material covering the lower and side surfaces of thewrite line is coated with the barrier layer having a function ofpreventing the diffusion of the atoms and the yoke material covering theupper and side surfaces of the data selection line is further coatedwith the barrier layer having the function of preventing the diffusionof atoms.

[0177] The element separation insulating layers 12 including the STIstructure are formed in the semiconductor substrate (such as the p-typesilicon substrate and p-type well region) 11. The region surrounded withthe element separation insulating layers 12 is the element region inwhich the read selection switch is formed.

[0178] The read selection switch is constituted of the MOS transistor(n-channel type MOS transistor). The gate insulating layer 13, gateelectrode 14, and side wall insulating layers 15 are formed on thesemiconductor substrate 11. The gate electrode 14 extends in theX-direction, and functions as the read word line for selecting the readcell (MTJ element) at the read operation time.

[0179] The source region (e.g., n-type diffusion layer) 16-S and drainregion (e.g., n-type diffusion layer) 16-D are formed in thesemiconductor substrate 11. The gate electrode (read word line) 14 isdisposed on the channel region between the source region 16-S and drainregion 16-D.

[0180] One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

[0181] The intermediate layer 18A is electrically connected to the drainregion 16-D of the read selection switch (MOS transistor) by the contactplug 17A. The source line 18B is electrically connected to the sourceregion 16-S of the read selection switch via the contact plug 17B. Thesource line 18B extends in the X-direction, for example, similarly asthe gate electrode (read word line) 14.

[0182] One of the metal layers constituting the second metal wiringlayer functions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

[0183] The lower surfaces of the intermediate layer 20A and write wordline 20B are coated with the material having the high permeability, thatis, yoke materials 25A1, 25B1.

[0184] The barrier metals (e.g., Ti, TiN, or the lamination of these) 27a, 27 b are formed right under the yoke materials 25A1, 25B1, and thebarrier metals (e.g., Ti, TiN, or the lamination of these) 27 c, 27 dare formed right on the barrier metals. That is, the yoke materials25A1, 25B1 are held between the barrier metals 27 a, 27 b, 27 c, 27 d.

[0185] Moreover, the side surfaces of the intermediate layer 20A andwrite word line 20B are also coated with the materials which have highpermeability, that is, yoke materials 25A2, 25B2.

[0186] When the yoke materials 25A1, 25B1, 25A2, 25B2 are used as thetraction material of the magnetic force line, the magnetic field Hygenerated by the write current flowing through the write word line 20Bcan efficiently be concentrated on the MTJ element 23.

[0187] The barrier layers 28 a, 28 b (e.g., Ti, TiN, or the laminationof these, or Ta, TaN, or the lamination of these) are formed on the sidesurfaces of the intermediate layer 20A and write word line 20B. Thebarrier layers 28 a, 28 b separate the yoke materials 25A1, 25B1 withwhich the lower surfaces of the intermediate layer 20A and write wordline 20B are coated from the yoke materials 25A2, 25B2 with which theside surfaces are coated.

[0188] The barrier layers 28 a, 28 b may have either the conductivity orinsulation property. Moreover, the barrier layers 28 a, 28 b may havethe same functions as those of the barrier metals 27 a, 27 b.

[0189] Additionally, when the atoms of the materials constituting theyoke materials 25A1, 25B1, 25A2, 25B2 reach the semiconductor substrate11 by the diffusion, the characteristics of the read selection switch(MOS transistor) formed on the surface region of the semiconductorsubstrate 11 are sometimes adversely affected.

[0190] To solve the problem, in the second embodiment, the yokematerials 25A1, 25B1, 25A2, 25B2 are coated with the barrier layer (suchas SiN) 34 which has the function of preventing the diffusion of atoms.Thereby, the diffusion of the atoms of the materials constituting theyoke materials 25A1, 25B1, 25A2, 25B2 is suppressed.

[0191] It is to be noted that the barrier layer 34 is constituted of aninsulating material. Additionally, the barrier layer 34 may also beconstituted of the conductive material, if the problem of short-circuitbetween the wires disposed adjacent to each other can be solved.

[0192] One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

[0193] One of the metal layers constituting the fourth metal wiringlayer functions as the data selection line (read/write bit line) 24. Thedata selection line 24 is electrically connected to the MTJ element 23,and extends in the Y-direction.

[0194] The upper surface of the data selection line 24 is coated withthe material having the high permeability, that is, the yoke material26. The barrier metal (e.g., Ti, TiN, or the lamination of these) 29 isformed on the lower surface of the data selection line 24, and thebarrier layer (e.g., Ti, TiN, or the lamination of these, or Ta, TaN, orthe lamination of these) 30 is formed on the upper surface of the dataselection line.

[0195] Moreover, the side surface of the data selection line 24 is alsocoated with the material which has the high permeability, that is, theyoke materials 32.

[0196] When the yoke materials 26, 32 are used as the traction materialof the magnetic force line, the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beconcentrated on the MTJ element 23.

[0197] The barrier layers 31 (e.g., Ti, TiN, or the lamination of these,or Ta, TaN, or the lamination of these) are formed on the side surfacesof the data selection line 24. The barrier layers 31 separate the yokematerial 26 with which the upper surface of the data selection line 24is coated from the yoke materials 32 with which the side surfaces of thedata selection line are coated.

[0198] The barrier layers 30, 31 may have either the conductivity orinsulation property. Moreover, the barrier layers 30, 31 may have thesame functions as those of the barrier metal 29.

[0199] Also with respect to the yoke materials 26, 32, similarly as theyoke materials 25A1, 25B1, 25A2, 25B2 with which the write word line 20Bis coated, when the atoms of the materials constituting the yokematerials reach the semiconductor substrate 11 by the diffusion, thecharacteristics of the read selection switch (MOS transistor) formed inthe surface region of the semiconductor substrate 11 are sometimesadversely affected.

[0200] To solve the problem, the yoke materials 26, 32 are coated withbarrier layer (such as SiN) 35 which has the function of preventing thediffusion of atoms. Thereby, the diffusion of the atoms of the materialsconstituting the yoke materials 26, 32 is suppressed.

[0201] It is to be noted that the barrier layer 35 is constituted of theinsulating material. Additionally, the barrier layer 35 may also beconstituted of the conductive material, if the problem of short-circuitbetween the wires disposed adjacent to each other can be solved.

[0202] (2) Manufacturing Method

[0203] The manufacturing method of the magnetic random access memoryaccording to the second embodiment of the present invention will next bedescribed.

[0204] First, as shown in FIG. 20, the methods such as the PEP, CVD, andCMP methods are used to form the element separation insulating layer 12including the STI structure in the semiconductor substrate 11.

[0205] Moreover, the MOS transistor as the read selection switch isformed in the element region surrounded with the element separationinsulating layer 12.

[0206] After forming the gate insulating layer 13 and gate electrode(read word line) 14 by the CVD, PEP, and RIE methods, the source region16-S and drain region 16-D are formed by an ion implantation method, sothat the MOS transistor can easily be formed. The side wall insulatinglayers 15 may also be formed on side wall portions of the gate electrode14 by the CVD and RIE methods.

[0207] Thereafter, the insulating layer 28A with which the MOStransistor is completely coated is formed by the CVD method. Moreover,the surface of the insulating layer 28A is flatted using the CMP method.The contact holes reaching the source region 16-S and drain region 16-Dof the MOS transistor are formed in the insulating layer 28A using thePEP and RIE methods.

[0208] The barrier metals (e.g., Ti, TiN, or the lamination of these) 51are formed on the insulating layer 28A and on the inner surfaces of thecontact holes by the sputter method. Continuously, the conductivematerials (e.g., the conductive polysilicon film including theimpurities, metal film, and the like) with which the contact holes arecompletely filled are formed on the insulating layer 28A by the sputtermethod. Moreover, by the CMP method, the conductive materials andbarrier metals 51 are polished, and the contact plugs 17A, 17B areformed.

[0209] The insulating layer 28B is formed on the insulating layer 28Ausing the CVD method. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 28B. The sputter method is usedto form the barrier metals (e.g., Ti, TiN, or the lamination of these)52 on the insulating layer 28B and on the inner surfaces of the wiringtrenches. Continuously, the conductive materials (e.g., the metal filmssuch as aluminum and copper) with which the wiring trenches arecompletely filled are formed on the insulating layer 28B by the sputtermethod. Thereafter, by the CMP, the conductive materials and barriermetals 52 are polished, and the intermediate layer 18A and source line18B are formed.

[0210] Subsequently, the CVD method is used to form the insulating layer28C on the insulating layer 28B. The PEP and RIE methods are used toform the via holes in the insulating layer 28C. By the sputter method,the barrier metals (e.g., Ti, TiN, or the lamination of these) 53 areformed on the insulating layer 28C and on the inner surfaces of the viaholes. Continuously, by the sputter method, the conductive materials(e.g., the metal films such as aluminum and copper) with which the viaholes are completely filled are formed on the insulating layer 28C.Thereafter, by the CMP method, the conductive materials and barriermetals 53 are polished, and the via plug 19 is formed.

[0211] Subsequently, as shown in FIG. 21, by the sputter method, thebarrier metals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27a, 27 b are formed on the insulating layer 28C. Subsequently, thesputter method is used to form the yoke materials (e.g., NiFe) 25A1,25B1 which have the high permeability in a thickness of about 50 nm onthe barrier metals 27 a, 27 b. Moreover, the sputter method is used toform the barrier metals (e.g., the lamination of Ti (10 nm) and TiN (10nm)) 27 c, 27 d on the yoke materials 25A1, 25B1.

[0212] Furthermore, the sputter method is continuously used to form theconductive material (e.g., AlCu) in a thickness of about 250 nm on thebarrier metals 27 c, 27 d. Thereafter, the PEP and RIE methods are usedto etch the conductive materials, yoke materials 25A1, 25B1, and barriermetals 27 a, 27 b, 27 c, 27 d, so that the intermediate layer 20A andwrite word line 20B are formed.

[0213] Additionally, the sputter method is used to form the barrierlayers (e.g., the lamination of Ta (10 nm) and TaN (10 nm)) 28 a, 28 bwith which the intermediate layer 20A and write word line 20B arecoated. The sputter method is continuously used to form the yokematerials (e.g., NiFe) 25A2, 25B2 which have the high permeability in athickness of about 50 nm on the barrier layers 28 a, 28 b.

[0214] Moreover, by the RIE method, the yoke materials 25A2, 25B2 andbarrier layers 28 a, 28 b are etched, so that the yoke materials 25A2,25B2 and barrier layers 28 a, 28 b remain only on the side wall portionsof the intermediate layer 20A and write word line 20B.

[0215] Thereafter, the CVD method is used to form the barrier layer(such as SiN) 34 with which the yoke materials 25Al, 25B1, 25A2, 25B2are coated in a thickness of about 20 nm. The CVD method is continuouslyused to form the insulating layer 29A with which the intermediate layer20A and write word line 20B are completely coated on the barrier layer34. Moreover, for example, by the CMP method, the surface of theinsulating layer 29A is flatted.

[0216] Subsequently, as shown in FIG. 22, the PEP and RIE methods areused to form the via holes which reach the intermediate layer 20A in theinsulating layer 29A. By the sputter method, the barrier metals (e.g.,Ti, TiN, or the lamination of these) 55 are formed on the insulatinglayer 29A and on the inner surfaces of the via holes in a thickness ofabout 10 nm. Continuously, the conductive materials (e.g., the metalfilm such as tungsten) with which the via holes are completely filledare formed on the insulating layer 29A by the CVD method. Thereafter, bythe CMP method, the conductive materials and barrier metals 55 arepolished, and the via plug 21 is formed.

[0217] The CVD method is used to form the insulating layer 30A on theinsulating layer 29A. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 30A. By the sputter method, theconductive materials (e.g., the metal films such as Ta) with which thewiring trenches are completely filled are formed in a thickness of about50 nm on the insulating layer 30A. Thereafter, by the CMP, theconductive materials are polished, and the local interconnect line(lower electrode of the MTJ element) 22 is formed.

[0218] The CVD method is used to successively deposit a plurality oflayers on the local interconnect line. 22, and these plurality of layersare further patterned to form the MTJ elements 23.

[0219] The CVD method is used to form the insulating layer 30B withwhich the MTJ element 23 is coated, and subsequently, the insulatinglayer 30B on the MTJ element 23 is removed, for example, by the CMPmethod. As a result, the topmost layer of the MTJ element 23 is exposed,and only the side surfaces of the MTJ element 23 are coated with theinsulating layer 30B.

[0220] It is to be noted that to constitute the topmost layer of the MTJelement 23 by Ta or W, the topmost layer of the MTJ element 23 isexposed, and subsequently the data selection line described later candirectly be formed.

[0221] Subsequently, as shown in FIG. 23, the barrier metal (e.g., thelamination of Ti (10 nm) and TiN (10 nm)) 29 is formed on the insulatinglayer 30B by the sputter method. Continuously, the conductive material(such as AlCu) is formed in a thickness of about 400 nm on the barriermetal 29 by the sputter method. Continuously, the barrier layer (e.g.,the lamination of Ta (10 nm) and TaN (10 nm)) 30 is formed on theconductive material by the sputter method.

[0222] Furthermore, the yoke material (such as NiFe) 26 which has thehigh permeability is continuously formed in a thickness of about 50 nmon the barrier layer 30 by the sputter method. Thereafter, the PEPmethod is used to form the resist pattern 33.

[0223] Additionally, the RIE method is used, and the resist pattern 33is used as the mask to etch the yoke material 26, barrier layer 30,conductive material, and barrier metal 29, so that the data selectionline (read/write bit line) 24 is formed.

[0224] Thereafter, the resist pattern 33 is removed.

[0225] Subsequently, as shown in FIG. 24, the barrier layer (e.g., thelamination of Ta (10 nm) and TaN (10 nm)) 31 with which the dataselection line 24 is coated is formed on the insulating layer 30B by thesputter method. Continuously, the yoke material (such as NiFe) 32 whichhas the high permeability is formed in a thickness of about 50 nm on thebarrier layer 31 by the sputter method.

[0226] Moreover, when the yoke material 32 and barrier layer 31 areetched by the RIE method, as shown in FIG. 25, the yoke material 32 andbarrier layer 31 remain only on the side wall portions of the dataselection line 24.

[0227] Furthermore, as shown in FIG. 25, the CVD method is used to formthe barrier layer (such as SiN) with which the yoke materials 26, 32 arecoated in a thickness of about 20 nm.

[0228] The magnetic random access memory of the second embodiment (FIGS.18 and 19) is completed by the above-described steps.

(3) CONCLUSION

[0229] As described above, according to the second embodiment, the yokematerials 25A1, 25A2, 25B1, 25B2 with which the lower and side surfacesof the intermediate layer 20A and write word line 20B are coated arefurther coated with the barrier layer 34 which has the function ofpreventing the diffusion of atoms. Moreover, the yoke materials 26, 32with which the upper and side surfaces of the data selection line 24 arecoated are further coated with the barrier layer 35 which has thefunction of preventing the diffusion of atoms.

[0230] Therefore, the atoms of the materials constituting the yokematerials 25A1, 25A2, 25B1, 25B2, 26, 32 can be inhibited from beingdiffused in the semiconductor substrate 11, and the characteristics ofthe MOS transistor can be prevented from being deteriorated.

[0231] 5. Third Embodiment

[0232]FIGS. 26 and 27 show the device structure of the magnetic randomaccess memory according to a third embodiment of the present invention.It is to be noted that FIG. 26 shows the section of the Y-direction, andFIG. 27 shows the section of the X-direction of the MTJ element portionof FIG. 26. The X-direction crosses at right angles to the Y-direction.

[0233] The device structure of the present embodiment is characterizedin that hard masks (such as SiO₂) are formed as masks at a wiringprocessing time right on the write word line and data selection line.

[0234] The element separation insulating layers 12 including the STIstructure are formed in the semiconductor substrate (such as the p-typesilicon substrate and p-type well region) 11. The region surrounded withthe element separation insulating layers 12 is the element region inwhich the read selection switch is formed.

[0235] The read selection switch is constituted of the MOS transistor(n-channel type MOS transistor). The gate insulating layer 13, gateelectrode 14, and side wall insulating layers 15 are formed on thesemiconductor substrate 11. The gate electrode 14 extends in theX-direction, and functions as the read word line for selecting the readcell (MTJ element) at the read operation time.

[0236] The source region (e.g., n-type diffusion layer) 16-S and drainregion (e.g., n-type diffusion layer) 16-D are formed in thesemiconductor substrate 11. The gate electrode (read word line) 14 isdisposed on the channel region between the source region 16-S and drainregion 16-D.

[0237] One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

[0238] The intermediate layer 18A is electrically connected to the drainregion 16-D of the read selection switch (MOS transistor) by the contactplug 17A. The source line 18B is electrically connected to the sourceregion 16-S of the read selection switch via the contact plug 17B. Thesource line 18B extends in the X-direction, for example, similarly asthe gate electrode (read word line) 14.

[0239] One of the metal layers constituting the second metal wiringlayer functions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

[0240] The lower surfaces of the intermediate layer 20A and write wordline 20B are coated with the material having the high permeability, thatis, yoke materials 25A1, 25B1.

[0241] The barrier metals (e.g., Ti, TiN, or the lamination of these) 27a, 27 b are formed right under the yoke materials 25A1, 25B1, and thebarrier metals (e.g., Ti, TiN, or the lamination of these) 27 c, 27 dare formed right on the barrier metals. That is, the yoke materials25A1, 25B1 are held between the barrier metals 27 a, 27 b, 27 c, 27 d.

[0242] Moreover, the side surfaces of the intermediate layer 20A andwrite word line 20B are also coated with the materials which have highpermeability, that is, yoke materials 25A2, 25B2.

[0243] When the yoke materials 25A1, 25B1, 25A2, 25B2 are used as thetraction material of the magnetic force line, the magnetic field Hygenerated by the write current flowing through the write word line 20Bcan efficiently be concentrated on the MTJ element 23.

[0244] The barrier layers 28 a, 28 b (e.g., Ti, TiN, or the laminationof these, or Ta, TaN, or the lamination of these) are formed on the sidesurfaces of the intermediate layer 20A and write word line 20B. Thebarrier layers 28 a, 28 b separate the yoke materials 25A1, 25B1 withwhich the lower surfaces of the intermediate layer 20A and write wordline 20B are coated from the yoke materials 25A2, 25B2 with which theside surfaces are coated.

[0245] The barrier layers 28 a, 28 b may have either the conductivity orinsulation property. Moreover, the barrier layers 28 a, 28 b may havethe same functions as those of the barrier metals 27 a, 27 b.

[0246] Hard masks (such as SiO₂) 36A, 36B constituting the masks at thewiring processing time (RIE time) are formed right on the intermediatelayer 20A and write word line 20B.

[0247] One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

[0248] One of the metal layers constituting the fourth metal wiringlayer functions as the data selection line (read/write bit line) 24. Thedata selection line 24 is electrically connected to the MTJ element 23,and extends in the Y-direction.

[0249] The upper surface of the data selection line 24 is coated withthe material having the high permeability, that is, the yoke material26. The barrier metal (e.g., Ti, TiN, or the lamination of these) 29 isformed on the lower surface of the data selection line 24, and thebarrier layer (e.g., Ti, TiN, or the lamination of these, or Ta, TaN, orthe lamination of these) 30 is formed on the upper surface of the dataselection line.

[0250] Moreover, the side surface of the data selection line 24 is alsocoated with the material which has the high permeability, that is, theyoke materials 32.

[0251] When the yoke materials 26, 32 are used as the traction materialof the magnetic force line, the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beconcentrated on the MTJ element 23.

[0252] The barrier layers 31 (e.g., Ti, TiN, or the lamination of these,or Ta, TaN, or the lamination of these) are formed on the side surfacesof the data selection line 24. The barrier layers 31 separate the yokematerial 26 with which the upper surface of the data selection line 24is coated from the yoke materials 32 with which the side surfaces of thedata selection line are coated.

[0253] The barrier layers 30, 31 may have either the conductivity orinsulation property. Moreover, the barrier layers 30, 31 may have thesame functions as those of the barrier metal 29.

[0254] A hard mask (such as SiO₂) 37 is formed as the mask at the wiringprocessing time (RIE time) right on the data selection line 24.

[0255] (2) Manufacturing Method

[0256] The manufacturing method of the magnetic random access memoryaccording to the third embodiment of the present invention will next bedescribed.

[0257] First, as shown in FIG. 28, the methods such as the PEP, CVD, andCMP methods are used to form the element separation insulating layer 12including the STI structure in the semiconductor substrate 11.

[0258] Moreover, the MOS transistor as the read selection switch isformed in the element region surrounded with the element separationinsulating layer 12.

[0259] After forming the gate insulating layer 13 and gate electrode(read word line) 14 by the CVD, PEP, and RIE methods, the source region16-S and drain region 16-D are formed by the ion implantation method, sothat the MOS transistor can easily be formed. The side wall insulatinglayers 15 may also be formed on side wall portions of the gate electrode14 by the CVD and RIE methods.

[0260] Thereafter, the insulating layer 28A with which the MOStransistor is completely coated is formed by the CVD method. Moreover,the surface of the insulating layer 28A is flatted using the CMP method.The contact holes reaching the source region 16-S and drain region 16-Dof the MOS transistor are formed in the insulating layer 28A using thePEP and RIE methods.

[0261] The barrier metals (e.g., Ti, TiN, or the lamination of these) 51are formed on the insulating layer 28A and on the inner surfaces of thecontact holes by the sputter method. Continuously, the conductivematerials (e.g., the conductive polysilicon film including theimpurities, metal film, and the like) with which the contact holes arecompletely filled are formed on the insulating layer 28A by the sputtermethod. Moreover, by the CMP method, the conductive materials andbarrier metals 51 are polished, and the contact plugs 17A, 17B areformed.

[0262] The insulating layer 28B is formed on the insulating layer 28Ausing the CVD method. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 28B. The sputter method is usedto form the barrier metals (e.g., Ti, TiN, or the lamination of these)52 on the insulating layer 28B and on the inner surfaces of the wiringtrenches. Continuously, the conductive materials (e.g., the metal filmssuch as aluminum and copper) with which the wiring trenches arecompletely filled are formed on the insulating layer 28B by the sputtermethod. Thereafter, by the CMP, the conductive materials and barriermetals 52 are polished, and the intermediate layer 18A and source line18B are formed.

[0263] Subsequently, the CVD method is used to form the insulating layer28C on the insulating layer 28B. The PEP and RIE methods are used toform the via holes in the insulating layer 28C. By the sputter method,the barrier metals (e.g., Ti, TiN, or the lamination of these) 53 areformed on the insulating layer 28C and on the inner surfaces of the viaholes. Continuously, by the sputter method, the conductive materials(e.g., the metal films such as aluminum and copper) with which the viaholes are completely filled are formed on the insulating layer 28C.Thereafter, by the CMP method, the conductive materials and barriermetals 53 are polished, and the via plug 19 is formed.

[0264] Subsequently, as shown in FIG. 29, by the sputter method, thebarrier metals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27a, 27 b are formed on the insulating layer 28C. Subsequently, thesputter method is used to form the yoke materials (e.g., NiFe) 25A1,25B1 which have the high permeability in a thickness of about 50 nm onthe barrier metals 27 a, 27 b. Moreover, the sputter method is used toform the barrier metals (e.g., the lamination of Ti (10 nm) and TiN (10nm)) 27 c, 27 d on the yoke materials 25A1, 25B1.

[0265] Furthermore, the sputter method is continuously used to form theconductive material (e.g., AlCu) in a thickness of about 250 nm on thebarrier metals 27 c, 27 d. Moreover, the sputter method is used to forminsulating layers (such as SiO₂) 36A, 36B as the hard masks in athickness of about 100 nm on the conductive material.

[0266] Thereafter, the resist pattern is formed by the PEP method.Moreover, the resist pattern is used as the mask to pattern theinsulating layers 36A, 36B as the hard masks by the RIE method.Thereafter, the resist pattern is removed.

[0267] Subsequently, this time the insulating layers 36A, 36B are usedas the masks to successively etch the conductive materials, yokematerials 25A1, 25B1, and barrier metals 27 a, 27 b, 27 c, 27 d by theRIE method, so that the intermediate layer 20A and write word line 20Bare formed.

[0268] Additionally, the sputter method is used to form the barrierlayers (e.g., the lamination of Ta (10 nm) and TaN (10 nm)) 28 a, 28 bwith which the intermediate layer 20A and write word line 20B arecoated. The sputter method is continuously used to form the yokematerials (e.g., NiFe) 25A2, 25B2 which have the high permeability in athickness of about 50 nm on the barrier layers 28 a, 28 b.

[0269] Moreover, by the RIE method, the yoke materials 25A2, 25B2 andbarrier layers 28 a, 28 b are etched, so that the yoke materials 25A2,25B2 and barrier layers 28 a, 28 b remain only on the side wall portionsof the intermediate layer 20A and write word line 20B.

[0270] Thereafter, the CVD method is used to form the insulating layer29A with which the intermediate layer 20A and write word line 20B arecompletely coated on the barrier layer 34. Moreover, for example, by theCMP method, the surface of the insulating layer 29A is flatted.

[0271] Subsequently, as shown in FIG. 30, the PEP and RIE methods areused to form the via holes which reach the intermediate layer 20A in theinsulating layer 29A. By the sputter method, the barrier metals (e.g.,Ti, TiN, or the lamination of these) 55 are formed on the insulatinglayer 29A and on the inner surfaces of the via holes in a thickness ofabout 10 nm. Continuously, the conductive materials (e.g., the metalfilm such as tungsten) with which the via holes are completely filledare formed on the insulating layer 29A by the CVD method. Thereafter, bythe CMP method, the conductive materials and barrier metals 55 arepolished, and the via plug 21 is formed.

[0272] The CVD method is used to form the insulating layer 30A on theinsulating layer 29A. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 30A. By the sputter method, theconductive materials (e.g., the metal films such as Ta) with which thewiring trenches are completely filled are formed in a thickness of about50 nm on the insulating layer 30A. Thereafter, by the CMP, theconductive materials are polished, and the local interconnect line(lower electrode of the MTJ element) 22 is formed.

[0273] The CVD method is used to successively deposit a plurality oflayers on the local interconnect line 22, and these plurality of layersare further patterned to form the MTJ elements 23.

[0274] The CVD method is used to form the insulating layer 30B withwhich the MTJ element 23 is coated, and subsequently, the insulatinglayer 30B on the MTJ element 23 is removed, for example, by the CMPmethod. As a result, the topmost layer of the MTJ element 23 is exposed,and only the side surfaces of the MTJ element 23 are coated with theinsulating layer 30B.

[0275] It is to be noted that to constitute the topmost layer of the MTJelement 23 by Ta or W, the topmost layer of the MTJ element 23 isexposed, and subsequently the data selection line described later candirectly be formed.

[0276] Subsequently, as shown in FIG. 31, the barrier metal (e.g., thelamination of Ti (10 nm) and TiN (10 nm)) 29 is formed on the insulatinglayer 30B by the sputter method. Continuously, the conductive material(such as AlCu) is formed in a thickness of about 400 nm on the barriermetal 29 by the sputter method. Continuously, the barrier layer (e.g.,the lamination of Ta (10 nm) and TaN (10 nm)) 30 is formed on theconductive material by the sputter method.

[0277] Furthermore, the yoke material (such as NiFe) 26 which has thehigh permeability is continuously formed in a thickness of about 50 nmon the barrier layer 30 by the sputter method. Moreover, the insulatinglayer (such as SiO₂) 37 which functions as the hard mask at the wiringprocessing time is formed on the yoke material 26 by the sputter method.Thereafter, the PEP method is used to form the resist pattern 33.

[0278] Additionally, the resist pattern 33 is used as the mask topattern the insulating layer 37 as the hard mask by the RIE method.Thereafter, the resist pattern 33 is removed.

[0279] Subsequently, as shown in FIG. 32, this time the insulating layer37 is used as the mask to successively etch the yoke material 26,barrier layer 30, conductive material, and barrier metal 29 by the RIEmethod, so that the data selection line (read/write bit line) 24 isformed.

[0280] Subsequently, as shown in FIG. 33, the barrier layer (e.g., thelamination of Ta (10 nm) and TaN (10 nm)) 31 with which the dataselection line 24 is coated is formed on the insulating layer 30B by thesputter method. Continuously, the yoke material (such as NiFe) 32 whichhas the high permeability is formed in a thickness of about 50 nm on thebarrier layer 31 by the sputter method.

[0281] Moreover, when the yoke material 32 and barrier layer 31 areetched by the RIE method, as shown in FIG. 34, the yoke material 32 andbarrier layer 31 remain only on the side wall portions of the dataselection line 24.

[0282] The magnetic random access memory of the third embodiment (FIGS.26 and 27) is completed by the above-described steps.

(3) CONCLUSION

[0283] As described above, according to the third embodiment, to processthe intermediate layer 20A and write word line 20B, the hard mask (suchas SiO₂) is used as the mask of RIE, not a photoresist. Therefore, atthe RIE time, an etching selection ratio can sufficiently be securedbetween the mask material, and the conductive material, yoke material,and barrier metal.

[0284] Similarly, also to process the data selection line 24, not thephotoresist, but the hard mask (such as SiO₂) is used as the mask ofRIE. Therefore, at the RIE time, the etching selection ratio cansufficiently be secured between the mask material, and the yokematerial, barrier layer, conductive material, and barrier metal.

[0285] 6. Fourth Embodiment

[0286]FIGS. 35 and 36 show the device structure of the magnetic randomaccess memory according to a fourth embodiment of the present invention.It is to be noted that FIG. 35 shows the section of the Y-direction, andFIG. 36 shows the section of the X-direction of the MTJ element portionof FIG. 35. The X-direction crosses at right angles to the Y-direction.

[0287] The device structure of the present embodiment is characterizedin that the yoke materials 25A1, 25A2, 25B1, 25B2 are constituted ofconductive materials, and the yoke materials 26, 32 and barrier layers28 a, 28 b, 30, 31 are constituted of insulating materials in the deviceof the first embodiment.

[0288] That is, the yoke materials 25A1, 25A2, 25B1, 25B2, 26, 32 andbarrier layers 28 a, 28 b, 30, 31 may also be constituted of theconductive or insulating materials.

[0289] 7. Fifth Embodiment

[0290]FIG. 37 shows the device structure of the magnetic random accessmemory according to a fifth embodiment of the present invention.

[0291] The device structure of the present embodiment is characterizedin that the structure of a write line in the first embodiment is appliedto the magnetic random access memory having a so-called ladder type cellarray structure.

[0292] In the ladder type cell array structure, a plurality of (four inthe present embodiment) MTJ elements 23 are arranged in a lateraldirection (direction parallel to the surface of the semiconductorsubstrate) on the semiconductor substrate 11. These MTJ elements 23 areconnected in parallel between the data selection line (read/write bitline) 24 and lower electrode.

[0293] One end of the MTJ element 23 is directly connected to the dataselection line 24, and the other end of the element is connected incommon to a read selection switch RSW via the lower electrode. Aplurality of MTJ elements 23 share one data selection line 24.

[0294] The data selection line 24 is disposed right on the plurality ofMTJ elements 23, and extends in the Y-direction. The upper surface ofthe data selection line 24 is coated with the yoke material 26 havingthe high permeability, and the side surfaces of the line are coated withthe yoke materials 32 having the high permeability.

[0295] The barrier layer 30 is disposed between the data selection line24 and yoke material 26, and the barrier layer 31 is disposed betweenthe data selection line 24 and yoke material 32. The barrier layer 31separates the yoke material 26 with which the upper surface of the dataselection line 24 is coated from the yoke materials 32 with which theside surfaces of the data selection line 24 are coated.

[0296] The barrier layers 30, 31 may have either the conductivity orinsulation property. Moreover, the barrier layers 30, 31 may have thesame functions as those of the barrier metal 29.

[0297] The write word line 20B is disposed right under the MTJ element23, and extends in the X-direction crossing at right angles to theY-direction. The lower surface of the write word line 20B is coated withthe yoke material 25B1 having the high permeability, and the sidesurfaces of the line are coated with the yoke material 25B2 having thehigh permeability.

[0298] The barrier layer 28 b is disposed between the write word line20B and yoke material 25B2. The barrier layer 28 b separates the yokematerial 25B1 with which the lower surface of the write word line 20B iscoated from the yoke materials 25B2 with which the side surfaces of thewrite word line 20B are coated.

[0299] The barrier layer 28 b may have either the conductivity orinsulation property. Moreover, the barrier layer 28 b may have the samefunction as that of the barrier metal 27 b.

[0300] It is to be noted that in the fifth embodiment the yoke materials25B1, 25B2, 26, 32, barrier metals 27 b, 27 d, and barrier layers 28 b,30, 31 may also be constituted of the conductive or insulatingmaterials.

[0301] 8. Sixth Embodiment

[0302]FIG. 38 shows the device structure of the magnetic random accessmemory according to a sixth embodiment of the present invention.

[0303] The device structure of the present embodiment is characterizedin that the structure of the write line in the first embodiment isapplied to the magnetic random access memory having another type of cellarray structure.

[0304] In the cell array structure, a plurality of (four in the presentembodiment) MTJ elements 23 are arranged in the Y-direction (directionparallel to the surface of the semiconductor substrate) on thesemiconductor substrate 11. These MTJ elements 23 are connected betweenthe write word line 20B extending in the X-direction and the upperelectrode.

[0305] One end of the MTJ element 23 is directly connected to the writeword line 20B, and the other end of the element is connected in commonto the read selection switch RSW via the upper electrode. A plurality ofMTJ elements 23 share one data selection line 24.

[0306] The data selection line 24 is disposed right on the plurality ofMTJ elements 23, and extends in the Y-direction. The upper surface ofthe data selection line 24 is coated with the yoke material 26 havingthe high permeability, and the side surfaces of the line are coated withthe yoke materials 32 having the high permeability.

[0307] The barrier layer 30 is disposed between the data selection line24 and yoke material 26, and the barrier layer 31 is disposed betweenthe data selection line 24 and yoke material 32. The barrier layer 31separates the yoke material 26 with which the upper surface of the dataselection line 24 is coated from the yoke materials 32 with which theside surfaces of the data selection line 24 are coated.

[0308] The barrier layers 30, 31 may have either the conductivity orinsulation property. Moreover, the barrier layers 30, 31 may have thesame functions as those of the barrier metal 29.

[0309] The write word line 20B is disposed right under the MTJ element23. The lower surface of the write word line 20B is coated with the yokematerial 25B1 having the high permeability, and the side surfaces of theline are coated with the yoke material 25B2.

[0310] The barrier layer 28 b is disposed between the write word line20B and yoke material 25B2. The barrier layer 28 b separates the yokematerial 25B1 with which the lower surface of the write word line 20B iscoated from the yoke materials 25B2 with which the side surfaces of thewrite word line 20B are coated.

[0311] The barrier layer 28 b may have either the conductivity orinsulation property. Moreover, the barrier layer 28 b may have the samefunction as that of the barrier metal 27 b.

[0312] It is to be noted that in the sixth embodiment the yoke materials25B1, 25B2, 26, 32, barrier metals 27 b, 27 d, 29 and barrier layers 28b, 30, 31 may also be constituted of the conductive or insulatingmaterials.

[0313] 9. Seventh Embodiment

[0314]FIG. 39 shows the device structure of the magnetic random accessmemory according to a seventh embodiment of the present invention.

[0315] The device structure of the present embodiment is characterizedin that the structure of the write line in the first embodiment isapplied to the magnetic random access memory having a so-called crosspoint type cell array structure.

[0316] In the cross point type cell array structure, a plurality of(four in the present embodiment) MTJ elements 23 are arranged in the Ylateral direction (direction parallel to the surface of thesemiconductor substrate) on the semiconductor substrate 11. These MTJelements 23 are connected between the data selection line (read/writebit line) 24 extending in the Y-direction and the write word line 20Bextending in the X-direction intersecting with the Y-direction.

[0317] One end of the MTJ element 23 is directly connected to the dataselection line 24, and the other end of the element is directlyconnected to the write word line 20B.

[0318] The data selection line 24 is disposed right on the plurality ofMTJ elements 23. The upper surface of the data selection line 24 iscoated with the yoke material 26 having the high permeability, and theside surfaces of the line are coated with the yoke materials 32 havingthe high permeability.

[0319] The barrier layer 30 is disposed between the data selection line24 and yoke material 26, and the barrier layer 31 is disposed betweenthe data selection line 24 and yoke material 32. The barrier layer 31separates the yoke material 26 with which the upper surface of the dataselection line 24 is coated from the yoke materials 32 with which theside surfaces of the data selection line 24 are coated.

[0320] The barrier layers 30, 31 may have either the conductivity orinsulation property. Moreover, the barrier layers 30, 31 may have thesame functions as those of the barrier metal 29.

[0321] The write word line 20B is disposed right under the MTJ element23. The lower surface of the write word line 20B is coated with the yokematerial 25B1 having the high permeability, and the side surfaces of theline are coated with the yoke material 25B2 having the highpermeability.

[0322] The barrier layer 28 b is disposed between the write word line20B and yoke material 25B2. The barrier layer 28 b separates the yokematerial 25B1 with which the lower surface of the write word line 20B iscoated from the yoke materials 25B2 with which the side surfaces of thewrite word line 20B are coated.

[0323] The barrier layer 28 b may have either the conductivity orinsulation property. Moreover, the barrier layer 28 b may have the samefunction as that of the barrier metal 27 b.

[0324] It is to be noted that in the seventh embodiment the yokematerials 25B1, 25B2, 26, 32, barrier metals 27 b, 27 d, and barrierlayers 28 b, 30, 31 may also be constituted of the conductive orinsulating materials.

[0325] 10. Others

[0326] In the description of the first, second reference examples, firstto seventh embodiments, and manufacturing method, the present inventionhas been described in terms of the examples of the cell array structurein which the memory cell is constituted of one MTJ element and one readselection switch, ladder type cell array structure, and cross point typecell array structure.

[0327] However, the present invention is not limited to the magneticrandom access memory of the cell array structure, and can be applied toall the magnetic random access memories including the device structuresshown in the first, second reference examples and first to seventhembodiments.

[0328] Moreover, the yoke materials on the upper or lower surface of thewrite line may be separated from the yoke materials on the side surfacesof the write line by the barrier layer. With the yoke material, all orsome of the surfaces of the write line excluding the surface on the MTJelement side may also be coated.

[0329] As described above, according to the magnetic random accessmemory of the embodiment of the present invention, since the yokematerial on the upper or lower surface of the write line is separatedfrom the yoke material on the side surface by the barrier layer, thefilm thickness and magnetic domain of the yoke material can easily becontrolled. At the write operation time, the synthetic magnetic fieldcan efficiently be exerted to the MTJ element.

[0330] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general invention concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A magnetic random access memory comprising: amemory cell which uses a magneto resistive effect to store data; a firstwrite line which is disposed right on the memory cell and which extendsin a first direction; a second write line which is disposed right underthe memory cell and which extends in a second direction intersectingwith the first direction; a first yoke material with which an uppersurface of the first write line is coated; a second yoke material withwhich a side surface of the first write line is coated; and a firstbarrier layer which is disposed between the first yoke material andfirst write line and between the second yoke material and first writeline and which separates the first yoke material from the second yokematerial.
 2. A magnetic random access memory according to claim 1,wherein the first barrier layer is disposed on the side surface of thefirst write line.
 3. A magnetic random access memory according to claim1, wherein the first barrier layer is constituted of a conductivematerial.
 4. A magnetic random access memory according to claim 1,wherein the first barrier layer is constituted of an insulatingmaterial.
 5. A magnetic random access memory according to claim 1,wherein the first barrier layer has a function of preventing diffusionof atoms constituting the first and second yoke materials.
 6. A magneticrandom access memory according to claim 1, further comprising: a secondbarrier layer disposed between the upper surface of the first write lineand the first yoke material.
 7. A magnetic random access memoryaccording to claim 6, wherein the second barrier layer is constituted ofa conductive material.
 8. A magnetic random access memory according toclaim 6, wherein the second barrier layer is constituted of aninsulating material.
 9. A magnetic random access memory according toclaim 6, wherein the second barrier layer has a function of preventingmutual diffusion of atoms constituting the first yoke material and atomsconstituting the first write line.
 10. A magnetic random access memoryaccording to claim 1, further comprising: a second barrier layer withwhich the first yoke material, second yoke material, and first writeline are coated.
 11. A magnetic random access memory according to claim10, wherein the second barrier layer is constituted of an insulatingmaterial.
 12. A magnetic random access memory according to claim 10,wherein the second barrier layer is constituted of a conductivematerial.
 13. A magnetic random access memory according to claim 10,wherein the second barrier layer has a function of preventing diffusionof atoms constituting the first and second yoke materials.
 14. Amagnetic random access memory according to claim 1, further comprising:a mask layer which is disposed on the first yoke material and which isused as a mask to pattern the first write line.
 15. A magnetic randomaccess memory according to claim 1, wherein the first write linecontacts the memory cell, and the second write line is apart from thememory cell.
 16. A magnetic random access memory according to claim 1,wherein the second write line contacts the memory cell, and the firstwrite line is apart from the memory cell.
 17. A magnetic random accessmemory according to claim 1, wherein the first and second write linesboth contact the memory cell.
 18. A magnetic random access memoryaccording to claim 1, wherein the memory cell is a TMR or GMR element.19. A magnetic random access memory according to claim 1, wherein thefirst barrier layer has a thickness of at least 20 nm.
 20. A magneticrandom access memory according to claim 6, wherein the second barrierlayer has a thickness of at least 20 nm.
 21. A magnetic random accessmemory according to claim 10, wherein the second barrier layer has athickness of at least 20 nm.
 22. A magnetic random access memorycomprising: a memory cell which uses a magneto resistive effect to storedata; a first write line which is disposed right on the memory cell andwhich extends in a first direction; a second write line which isdisposed right under the memory cell and which extends in a seconddirection intersecting with the first direction; a first yoke materialwith which a lower surface of the second write line is coated; a secondyoke material with which a side surface of the second write line iscoated; and a first barrier layer which is disposed between the firstyoke material and first write line and between the second yoke materialand first write line and which separates the first yoke material fromthe second yoke material.
 23. A magnetic random access memory accordingto claim 22, wherein the first barrier layer is disposed on the sidesurface of the second write line.
 24. A magnetic random access memoryaccording to claim 22, wherein the first barrier layer is constituted ofa conductive material.
 25. A magnetic random access memory according toclaim 22, wherein the first barrier layer is constituted of aninsulating material.
 26. A magnetic random access memory according toclaim 22, wherein the first barrier layer has a function of preventingdiffusion of atoms constituting the first and second yoke materials. 27.A magnetic random access memory according to claim 22, furthercomprising: a second barrier layer disposed between the lower surface ofthe second write line and the first yoke material.
 28. A magnetic randomaccess memory according to claim 27, wherein the second barrier layer isconstituted of a conductive material.
 29. A magnetic random accessmemory according to claim 27, wherein the second barrier layer isconstituted of an insulating material.
 30. A magnetic random accessmemory according to claim 27, wherein the second barrier layer has afunction of preventing mutual diffusion of atoms constituting the firstyoke material and atoms constituting the second write line.
 31. Amagnetic random access memory according to claim 22, further comprising:a second barrier layer with which the first yoke material, second yokematerial, and second write line are coated.
 32. A magnetic random accessmemory according to claim 31, wherein the second barrier layer isconstituted of an insulating material.
 33. A magnetic random accessmemory according to claim 31, wherein the second barrier layer isconstituted of a conductive material.
 34. A magnetic random accessmemory according to claim 31, wherein the second barrier layer has afunction of preventing diffusion of atoms constituting the first andsecond yoke materials.
 35. A magnetic random access memory according toclaim 22, further comprising: a mask layer which is disposed on thesecond write line and which is used as a mask to pattern the secondwrite line.
 36. A magnetic random access memory according to claim 22,wherein the first write line contacts the memory cell, and the secondwrite line is apart from the memory cell.
 37. A magnetic random accessmemory according to claim 22, wherein the second write line contacts thememory cell, and the first write line is apart from the memory cell. 38.A magnetic random access memory according to claim 22, wherein the firstand second write lines both contact the memory cell.
 39. A magneticrandom access memory according to claim 22, wherein the memory cell is aTMR or GMR element.
 40. A magnetic random access memory according toclaim 22, wherein the first barrier layer has a thickness of at least 20nm.
 41. A magnetic random access memory according to claim 27, whereinthe second barrier layer has a thickness of at least 20 nm.
 42. Amagnetic random access memory according to claim 31, wherein the secondbarrier layer has a thickness of at least 20 nm.
 43. A manufacturingmethod of a magnetic random access memory, comprising: forming a firstyoke material on an insulating layer on a semiconductor substrate;forming a conductive material on the first yoke material; patterning theconductive material and first yoke material; forming a write line whoselower surface is coated with the first yoke material; forming a firstbarrier layer with which the write line is coated; forming a second yokematerial with which the write line is coated on the first barrier layer;etching the first barrier layer and second yoke material; leaving thefirst barrier layer and second yoke material on the side surface of thewrite line; and forming a memory cell which uses a magneto resistiveeffect to store data right on the first write line.
 44. A manufacturingmethod according to claim 43, further comprising: forming a secondbarrier layer between the first yoke material and conductive material.45. A manufacturing method according to claim 43, further comprising:forming a second barrier layer with which the first yoke material,second yoke material, and write line are coated.
 46. A manufacturingmethod according to claim 43, wherein the patterning is executed by RIEin which a photoresist is used as a mask.
 47. A manufacturing methodaccording to claim 43, wherein the patterning is executed by RIE inwhich a silicon insulating layer is used as a mask.
 48. A manufacturingmethod according to claim 43, wherein the memory cell is formed in aposition apart from the write line.
 49. A manufacturing method accordingto claim 43, wherein the memory cell is formed in a position in contactwith the write line.
 50. A manufacturing method of a magnetic randomaccess memory, comprising: forming a memory cell which uses a magnetoresistive effect to store data on an insulating layer on a semiconductorsubstrate; forming a conductive material right on the memory cell;forming a first yoke material on the conductive material; patterning thefirst yoke material and conductive material; forming a write line whoseupper surface is coated with the first yoke material; forming a firstbarrier layer with which the write line is coated; forming a second yokematerial with which the write line is coated on the first barrier layer;etching the first barrier layer and second yoke material; and leavingthe first barrier layer and second yoke material on the side surface ofthe write line.
 51. A manufacturing method according to claim 50,further comprising: forming a second barrier layer between theconductive material and first yoke material.
 52. A manufacturing methodaccording to claim 50, further comprising: forming a second barrierlayer with which the first yoke material, second yoke material, andwrite line are coated.
 53. A manufacturing method according to claim 50,wherein the patterning is executed by RIE in which a photoresist is usedas a mask.
 54. A manufacturing method according to claim 50, wherein thepatterning is executed by RIE in which a silicon insulating layer isused as a mask.
 55. A manufacturing method according to claim 50,wherein the memory cell is formed in a position apart from the writeline.
 56. A manufacturing method according to claim 50, wherein thememory cell is formed in a position in contact with the write line.